1. Field of the Invention
The invention relates to technology of an incremental forming method.
2. Description of Related Art
According to an incremental forming method, a rod-shaped tool is pressed into a metal plate (i.e., a workpiece) and the workpiece is stretched little by little while moving the rod-shaped tool, without using a die. The incremental forming method is well known as a method used to form a workpiece, which is suitable for low-volume production (see Japanese Patent Application Publication No. 2006-341262 (JP 2006-341262 A), for example).
However, when performing incremental forming on a workpiece that has been formed (i.e., processed) by press-forming, for example, the stress distribution balance between the front and the back of the workpiece ends up changing. As a result, the amount of dimensional change in the workpiece before and after incremental forming increases. Therefore, a forming method capable of reducing the amount of dimensional change in a workpiece before and after forming, when incremental forming is performed, is needed.